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Back to the Future.

Milestones Back to the future

Back to the Future.

The 540 K streamlined saloon is not just a masterpiece of 1930s automotive construction, it is also of symbolic significance for Mercedes-Benz, because this two-door car can be considered a textbook example of the innovative strength of the brand and the inventiveness of its engineers. This makes the 540 K an unforgotten automobile, a legend on wheels.

With its at once aerodynamic and stylish body form, the 540 K streamlined saloon was unveiled in 1938 as a herald of the future. Although the time was not then ripe for applying such ideas to automotive series production, this one-off model had pioneering potential for subsequent passenger car development. This was true above all where aerodynamics was concerned. As such, the 540 K streamlined saloon provides a further example of Mercedes-Benz’s commitment and its philosophy of making its mark as the technological, conceptual and stylistic pacesetter in passenger car development. The faithful reconstruction and restoration of the 540 K streamlined saloon brought the glory of the 1930s back to life. It delivers impressive proof of the Mercedes-Benz Classic’s expertise and the authenticity of its work.

Mercedes-Benz Classic presents the Mercedes-Benz 540 K Streamliner to the general public – an exceptional vehicle that never ceases to amaze even the experts. Some 75 years after it was built, in 1938, the vehicle is back on the road. This is a unique vehicle, created at the time with the potential to compete in the Berlin-Rome long-distance race, which was first of all postponed to 1939 and then cancelled completely due to the outbreak of the Second World War. From mid-1938 onwards, the streamliner was used by the German branch of tyre manufacturer Dunlop for the relentless everyday testing of high-speed tyres for fast cars. Mothballed after the war, following full restoration to its original condition it is now about to be thrust into the limelight once more.

“The 540 K Streamliner is a prime example of the innovative automotive vehicle design of the 1930s, combining as it does exceptional efficiency with sophisticated, perfect aesthetics. Its emotionally appealing design idiom radiates luxury and glamour”, says Gorden Wagener, Vice President Design at Daimler AG. “As such this extraordinary vehicle provides the ideal link to vehicle design as we understand it today, emotionally appealing as well as intelligent, and synonymous with sophisticated luxury.”

To which Dr Teddy Woll, head of the Aerodynamics/Wind Tunnels department at Daimler AG, adds: “Tremendous advances were made in aerodynamics during the 1920s, and the influence of this thinking was felt more and more in vehicle development during the 1930s. The 540 K Streamliner of 1938 embodies the prevalent understanding of aerodynamics at that time in impressive style.”

The 540 K Streamliner was developed in the years 1937/38 in the special vehicle production department of the Mercedes-Benz Sindelfingen plant, under the direction of Hermann Ahrens. From today’s perspective the vehicle would be described as a Gran Turismo styled coupé, although the conventions of the 1930s meant that the designers depicted this body shape as a streamlined saloon, or quite simply ‘Streamliner’. The perfection of the design as a whole and of numerous individual technical details evidenced by this trailblazing vehicle exemplifies not only the innovative strength of the Mercedes-Benz brand, but also its expertise in the development of one-off models that set a true benchmark in design, comfort, quality and customer benefit.

This special vehicle, with its powerful supercharged engine, is designed to accelerate rapidly to a high speed and then, thanks to the aerodynamic lines developed in the wind tunnel, to maintain that speed. The whole is then enveloped in a sublime, streamlined body made of lightweight aluminium. This, combined with its powerful powertrain system, makes the 540 K a truly unique vehicle.

Measurements made in the wind tunnel in May 2014 revealed a drag coefficient of Cd = 0.36 – exquisite for a vehicle from the 1930s. A direct comparison with a standard-specification 540 K Coupé makes clear the leap made here in terms of aerodynamics: the figure for the coupé is Cd = 0.57.

In a highly challenging and complex restoration project undertaken by Mercedes-Benz Classic, the vehicle has now been rebuilt to its original condition. “We launched the project in 2011 and have been pressing forward with it at full throttle ever since”, commented Michael Bock, Head of Mercedes-Benz Classic. “It offers outstanding evidence of our expertise in the handling of automotive history.” Technical skills, methods and materials of the period from which the vehicle originates were used. The search for background information in the archives produced important documentary evidence, with the end result a spectacular one-off vehicle. The car stands today as it would have been seen in public in 1938: a herald of the future, whose high driving speeds and exceptional performance are quite apparent even when it is stationary. A unique, avant-garde messenger from an era still characterised by traditional bodywork styling, which has sped its way straight into the modern age, and still somehow looks up-to-date, even today.

The restoration of the 540 K Streamliner represents one of the most complex projects undertaken by Mercedes-Benz Classic. The starting signal was given at the end of 2011. Some important components of the original vehicle were preserved among the company’s own collection, for example the complete frame and the rear axle which, with higher speeds a key factor, featured a longer gear ratio. But of the most important component of this unique vehicle only traces remain on the frame: the streamlined aluminium body. And that is what makes this 540 K probably the most unusual 540 K in the world.

The project began, quite literally, to take shape at the point when the Mercedes-Benz Classic Archives made the original line drawing from their collection available. This established the precise dimensions of the vehicle – the drawing is a millimetre-precise three-dimensional surface description of the outer shell, developed on the drawing board. The wooden frame, the position of the radiator and the vehicle side members, along with other important details, are also shown here. The ideal opportunity thus presented itself to combine this historical information with sophisticated CAD technologies and so to transpose the surface description found in the archives to a contemporary medium. This then made it possible to add further details and, particularly importantly, to create manufacturing drawings, auxiliary tools and templates, so helping to ensure that the result was as true to the original as possible. This all sounds quite simple. Nevertheless, it took about a year to prepare for production. Once all the details had been brought together, the second starting signal for the project was given in early 2013: this allowed the building of the body and chassis and thus led ultimately – as once before in 1938 – to the assembly of the completed vehicle.

And then of course there was a need to find experts – experts with a mastery of the old craftsmanship skills required for working on classic cars. People, for example, who could build the wooden subframe, made out of ash wood, that supports the aluminium body. Who could shape this body shell, admittedly with some help from machines but largely by hand, with absolute precision and give it a perfectly smooth surface finish. People who could furnish the interior in walnut and finest cowhide, making the ambience of one of the most exclusive new cars of the 1930s tangible again. Who could rebuild the technical features of the 540 K in such a way that the vehicle would, as then, be able to reach and sustain high speeds with absolute reliability. In short: people who could recreate the 540 K exactly as it was when it was first built in 1938.

You can forget ‘standard’ in the case of the 540 K. Virtually every part that no longer existed, and every detail, needed to be individually made or tracked down in the Mercedes-Benz Classic collection. But that was ultimately part of the journey through time that this complex restoration project involved: for in 1938, when this vehicle was first built, it was also an individual, one-off creation. With one small difference, needless to say: while the special vehicle production unit at the Sindelfingen plant spent day in, day out and year after year building the very finest sort of exclusive cars, developing a certain routine as they did so, their modern-day successors at Mercedes-Benz Classic came up against the question time and time again at various stages of their work: How did they do that? They viewed this question, as became clear when you saw them at work, as part of the challenging task they faced to make the restoration of the vehicle as exact as possible.

Coupled with thorough research. For craftsmanship at Mercedes-Benz Classic is always flanked by a sound basis of knowledge provided by the archives. Documents were brought to light, for example the original quotation drawing for the streamliner, which provides an extremely detailed impression of what is perhaps the most unusual body ever set onto the chassis of a 540 K. Or the entry in the commission book, which documents the start of production along with customer data, as well as the original vehicle registration document, which reveals important dates from the life of this vehicle. Old photos appeared – not many, but each one of them a tremendous help along the way to achieving the perfect result. High-resolution scanning of the original glass negatives from the 1930s, for example, revealed the minutest of details, such as how the historical number plates were made, the shape of the dashboard and even the position of the screws used to mount the wooden trim in the interior. Further information was provided by the parts lists and owner’s manual for the 540 K. All these materials together made up a thick package of manufacturing documents over which the experts would cogitate together in the workshop, trying to understand the designs and manufacturing techniques of the 1930s and puzzling things out until they found the perfect solution. It is for this reason that this was not simply a restoration project, but was in some respects also a reconstruction project.

And its success was ultimately due to the teamwork between all those involved. A wide range of experts and skills worked here together, each contributing their knowledge of historical vehicle engineering and contemporary manufacturing methods – until the 540 K Streamliner could once again be seen in its original, pristine condition.

The reconstruction of the body

Time and time again the project involved the experts trying to work out the construction techniques of the 1930s, since no details or production steps for the body shell were to be found in the documentation. This makes this 540 K a perfect example of how to combine restoration and reconstruction.

The remaining parts – the frame, the rear axle with its longer gear ratio and the mountings for the wings – were repaired and preserved. They bear to this day the marks of time and so tell the story of the vehicle in their own way: signs of wear and tear, for example, show that the vehicle was not treated by Dunlop with any particular respect during tyre testing. Drill holes show how the underbody panelling was attached to the frame. And then there are the traces of paint: once upon a time, the vehicle was silver. The traces that remain provided the basis for mixing paintwork to match.

Just as it was in the 1930s, the vehicle was assembled in the classic way: a steel frame holding all the technical elements is surmounted by an ash-wood subframe that supports the body shell. This in its turn was built largely by hand, albeit with some help from machines – as it was back in days of the special vehicle production unit. Some 4800 hours of work were involved just in rebuilding the body. A design drawing was prepared for every single detail. Ultimately, the precision achieved is impressive: all the bodywork components fit together perfectly. And if the vehicle doors clunk satisfactorily into place and the panel gaps look narrow and even – then the rebuilt vehicle is a witness of its age and at the same time an ambassador for the highest standards of vehicle restoration. The “Sindelfinger Karosserie” badge on the left-hand side of the vehicle is once again a seal of quality for an individually produced vehicle of the highest quality.

Aerodynamics experts from the present-day passenger car development department at Mercedes-Benz provided advice on the reconstruction of the underbody panelling. Its design was determined by the original mounting points, as found on this special vehicle only, and is almost completely enclosed, with only ventilation slits under the engine, transmission and exhaust system.

Very little historical information or photographic material relating to the interior is available. What little there is was used, but in this case the reconstruction required considerable expertise. One thing is clear: the dashboard is curved in order to fit within the contours of the occupant compartment – and, just as then, it has once again been made produced in walnut. The same contours are followed by the two curved windscreens, reproduced in glass. The historical evidence tells us that the vehicle originally featured grey leather appointments with a grey fabric roof liner – after 76 years, the Streamliner now looks this way again. The two seats in the front correspond to the original, including the way the piping runs across the appropriately ruffled leather. Technical drawings show that folding seats were mounted in the rear – new ones have been created.

The Mercedes-Benz 540 K Streamliner was created in 1937/1938 in the special vehicle production unit at the company’s Sindelfingen plant. Over the course of the 1930s this unit had very quickly developed a reputation for the realisation of what were often very elaborate one-off vehicles, many of them with truly outstanding body designs. It was against this backdrop that plans for the 540 K with streamlined body evolved. Clearly, the car’s most important feature is its body shell, which in every detail meticulously reflects the understanding of aerodynamics that was prevalent at that time. Yet over and above this, and in conjunction with its extremely powerful supercharged engine, its designers were able to address the topic of (high) speed, sending a clear signal in this respect: the first fast roads had just been built, while the concept of fast and comfortable long-distance journeys by car was gradually edging its way into the public’s perception. So at the same time this special 540 K represents an example of an exceptional touring vehicle that is also more than capable of covering long distances at high speed. And it was as such that it was later used by Dunlop for high-speed tyre testing.

The plans produced by the special vehicle production unit show a design that was extremely advanced for the time, if not to say positively modern: a rounded front section with no bumper, featuring an almost square air intake without the usual, classic Mercedes-Benz radiator grille, deep-set headlamps in the left and right wing sections (merely hinted at here), then a long, stretched-out rear end that harmoniously links the tapered rear of the occupant cabin with a rounded, wedge-shaped body section. Even the classic Mercedes star adorning the radiator has been surrendered to the flowing, aerodynamic lines and is merely painted onto the front of the bonnet.

The third headlamp, a convention of the time that was commonly referred to as the “autobahn light”, is positioned in the centre of the radiator grille lattice, more or less where the large central star is located on many of today’s Mercedes-Benz vehicles. The rear wheel arches with their integrated wings, together with underbody panelling, have a similar positive impact on the aerodynamics. The windscreen is set at a slight angle and curved at either side, rather like the experimental cars used by the FKFS (Research Institute of Automotive Engineering and Vehicle Engines Stuttgart) at around the same time. This ran counter to the patented Jaray Line and its dogma of semi-circular curves; but a licence for use of the Jaray patent was not used for the body, which was instead all the work of the special vehicle production unit’s own bodywork designers. Of the 540 K Streamliner the unit head, Hermann Ahrens, wrote later: “Shape developed in wind tunnel”. Since the aerodynamic properties of the company’s racing cars had been measured in the wind tunnel since the early 1930s, before completion of the final stages of development, it is absolutely possible that a model of the 540 K could have been measured at that time in a German wind tunnel. Options available would have been the Aerodynamische Versuchsanstalt (AVA, Aerodynamics Research Institute) in Göttingen, the Deutsche Versuchsanstalt für Luftfahrt (DVL, German Aviation Laboratory) in Berlin-Adlershof or the Zeppelin wind tunnel in Friedrichshafen.

One should not think that the development division at Daimler-Benz at that time was always conservative in its approach. In the technical field there were certainly some extremely progressive ideas for the proposed production vehicles of the future. Automated transmissions, 5-speed gearshifts and steering-wheel gearshifts are just a few examples of the readiness to innovate found there. These were joined at a relatively early stage by several experimental vehicles with streamlined bodies, for some of which we even have the Cd values, a fact that indicates that these experimental developments did indeed see the inside of a wind tunnel. Among the designers of these bodies we find, for example, bodywork engineer Erich Uebelacker. He had worked for the Czech company Tatra on the development of their first standard-production streamlined model, the Type 77, which had first appeared at the end of 1933 and was considered a sensation in Europe at the time.

When it came to the engines, Daimler-Benz had experimented early on with engines in a horizontally opposed or V configuration. Tests were also made with the mid-engine, while even front-wheel drive was not omitted from consideration. Internal company documents point out time and time again the importance of the streamlined body, despite the oft-repeated emphasis on the significance of the “classic” Mercedes-Benz radiator. In this respect we can also concede the strong influence on later developments of the car presented here, for its styling already almost anticipates the later face of the 300 SL of 1952, built initially as a racing sports car. The later designer of the 300 SL production sports car, Friedrich Geiger, had been entrusted with important aspects of work in the special vehicle production unit as early as the 1930s and is bound to have internalised the basic front-end design. That the thinking had advanced even further by the time of the one-off 540 K Streamliner is made clear by a further body shell design based on this vehicle, which is configured as a cabriolet but in essence retains the same basic lines. So it is almost as if this car could have been a potential precursor of a whole series of further, aerodynamically designed series-production models.